Dementia is a form of thought disorder affecting the memory. When a doctor judges that a patient's mental impairment is too severe for the individual to live without supervision, this is known as clinical dementia. Doctors use the clinical dementia rating (CDR) to evaluate the degree of a patient's dementia. Other methods of evaluating dementia are memory tests, mental status examinations, and problem-solving tasks.
The CDR is based on a project on memory and aging that was created by the School of Medicine at Washington University in Missouri. In this project, a scale of five ratings is used to classify the severity of the dementia. Zero indicates no dementia, 0.5 indicates possible dementia, 1 is mild dementia, 2 is moderate dementia, and 3 is severe dementia.
Six different domains are used to evaluate mental function. They are memory, orientation, judgment and problem-solving, community affairs, home and hobbies, and personal care. Each domain is given its own row on a chart, with the severity scale running across the top, and each domain was given a rating. These scores were then added together to produce an overall dementia rating. The chart was gave an overview of an individual's overall mental competence.
The clinical dementia rating chart is developed from responses to a 10-page questionnaire. The patient — or caretaker if the patient is unresponsive — answers questions about his or her ability to understand common instructions. Questions can refer to the current date, the ability to handle money, grooming, and other factors of daily living.
This rating system has been standardized by clinics and hospitals for the evaluation of different types of dementia. It is commonly used to evaluate dementia in the elderly arising from Alzheimer’s. The system can also be used to evaluate other forms of dementia, such as those arising from alcoholism, Parkinson’s disease, or from an acquired immune deficiency disease such as AIDS.
The clinical dementia rating is not generally used to evaluate for alteration of consciousness, such as that arising from head injuries or organ toxicity. This is because it has been designed to evaluate mental status independent of physical condition. The clinical dementia rating questionnaire has been found to have a high correlation with memory tests and examinations such as the mini-mental state examination (MMSE). For example, it was found that those who had high scores on these types of tests also scored well on the CDR exam, and vice versa.